Most underrated happy hour?
My friends and I like hanging out at Barton Springs Saloon. Their happy hour prices are really just on well drinks but they make up for it with their Monday $1 Lone Star longnecks, Tues $1 Miller Hi Life longnecks, Wed $1 Natty Lite longnecks and Sunday $2 vodka drinks all day. I also enjoy going to Oil Can Harry's on Friday for happy hour cheap & strong drinks plus the buffet...yes, buffet. The buffet is decent considering it's basically free (please tip). Another place is Saba, which can get crowded on Fridays but other weeknights is nicely full as opposed to squished in at the bar. Plus they have some half price appies, too.
I second Saba Blue - they have huge bar; the six or so times I've been there for weekday happy hour they don't get busy until after 6pm or later. About the same time that live music kicks off at the nearby courtyard.
Notable to me: Their Rojo Mojito for $4 is a great drink, the Michelada is also a good deal at $2.50 with Mexican lager beer and great tomato mix (Zing Zang enhanced) on the side.